The present invention is directed generally to novel systems and methods for performing ion beam sputter deposition (IBSD), and to optical devices manufactured using such systems and methods.
The present invention relates to ion beam sputter deposition (IBSD). More particularly, the present invention concerns a system and method for performing sputter deposition using a divergent ion beam source. It is believed that IBSD is a common technique in the manufacturing of optical filters.
The method is normally carried out in a vacuum environment by bombarding a target with ion current. The bombardment results in the dislodging of atoms from the target which are then deposited as a film on a substrate. IBSD is an improvement over other types of sputter deposition techniques because it produces films of high quality with improved adhesive properties. IBSD procedures sputtered films that have a density very similar to the bulk density of the materials used and a surface roughness which is equal to that of a super-polished substrate. These results are advantageous for optical coatings.
Performance of optical filters is further improved with deposition thickness that is uniform across the substrate. The disclosed system and method provide such an improvement.
The present invention is directed to a system for performing sputter deposition on a substrate. A divergent ion current source generates a divergent ion beam. The ion current source has a central axis about which ions are directed toward a surface of a negatively biased target. A rotating substrate is positioned proximate to the target. The central axis of the ion current source is normal to the surface of the target and parallel to a deposition surface of the rotating substrate. In one embodiment, the magnitude of ion current produced by the ion current source varies throughout the ion beam in accordance with the equation ion current =Jo cos (xcex8); where xcex8 is an angle between the central axis of the ion source and a direction of the ion current, and Jo is the ion current density along the central axis.
In one embodiment, the central axis of the ion current sources intersects the center of the target. The target has a length and the substrate rotates about a rotational axis. In this embodiment, the surface of the substrate may be spaced from the central axis by half of the target length, and the surface of the target may be spaced from the rotational axis by half the target length.
Still another aspect of the invention is an optical filter, which is created by the disclosed method and process. The optical filter comprises a substrate, and material deposited on the substrate by the disclosed process and method.